Chain saw attachment



April1-1959 1 c. M. WALKER 3,435,859

CHAIN SAW ATTACHMENT Filed March 22, 1968 CHARLES M. WALKER United States Patent O 3,435,859 CHAIN SAW ATTACHMENT Charles M. Walker, R.R. 1, Greensburg, Ind. 47240 Filed Mar. 22, 1968, Ser. No. 715,332 Int. Cl. B27b 17/14 U.S. Cl. 143--32 6 Claims ABSTRACT OF THE DISCLOSURE A chain saw chain tensioner including a coil spring acting to rotate a screw through a toothed clutch. The screw has mounted thereon a lug member which functions to urge a blade against the saw chain to tension it, the urging force being provided by the coil spring.

Background of the invention Field of the invention-This invention relates to a chain saw tensioner device.

Description of the prior art-Various devices for controlling and maintaining the tension of the chain in a chain saw are known in the art. Suc-h devices are disclosed, for example, in the following prior art patents: Walker, 3,194,284; Shade, 2,357,230; Arneson, 2,624,379; Van Ausdall, 2,645,254; and Siria 2,839,097.

Summary of the invention One embodiment of the invention might include, in a chain saw including an endless toothed chain, a frame, a drive sprocket rotatably mounted on said frame and supporting said chain, a pair of spaced threaded studs fixed to said frame, a blade having an elongated]` slot and received on said studs with the studs projecting through `said slot, a guard cover received on said studs, nuts retaining said cover on said studs, a spacer having a thickness greater than the thickness of said blade and received between said frame and cover and spacing said cover from said frame a sufficient distance to permit reciprocation of said blade on said studs, said blade providing supporting means for said chain, the improvement which comprises: a screw rotatablymounted on and extending through said cover and having an enlarged headed end bearing against said cover, a` lug member threadedly received on said screw, said lug member having a lug projecting perpendicularly of said blade, said blade having an aperture receiving the lug of said lug member, said screw having an extension secured thereto which is coaxial with said screw, a coil spring coiled about said extension and xed at one end to said cover, a clutch including two portions one of which is lixedly mounted on the distal end of said spring and the other of which is iixedly mounted on said extension, said coil spring acting to resiliently hold said clutch portions in engagement with one another, said clutch portions being capable of holding in the same relative position to one another against forces below a given magnitude tend ing to rotate one portion relative to the other, but arranged to permit relative rotation of said portions in response to Iforces albove said given magnitude tending to rotate oneportion relative to the other.

One object of this invention is to provide an improved chain saw tensioning device.

Another object of this invention is to provide a chain saw tensioning device which is operable to set the chain tension at a desired value and which is also operable to maintain the tension on the chain.

Related objects and advantages will appear as the description proceeds.

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Brief description of the drawing The full nature of the invention will be understood from the accompanying dra-wings and the following description and claims.

FIGURE 1 is a side elevation of a chain saw incorporating the present invention.

vFIGURE 2 is an enlarged view similar to FIGURE 1 with the cover or cover plate of the chain saw removed.

FIGURE 3 is a fragmentary section taken along the line 3-3 of FIGURE 2 in the direction of the arrows.

FIGURE 4 is a detail view of the inside portion of the cover or cover plate of FIGURE 1.

Description of the preferred embodiment For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawing and specilic language will be used to describe the same. It will nevertireless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modiiications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

Referring now more particularly to the drawings, there is illustrated a chain saw 1|) including the usual frame 11 having a motor 12 (which in the illustrated embodiment is a gasoline motor) mounted thereon. The saw is provided with conventional handles 15 and 16 ixed to the motor and frame. The frame includes a at quadrilateral plate portion 17 which is bordered on two sides by a guard 18, the guard 18 being in the form of a flange which projects perpendicularly relative to the plate portion 17 and protects the users hands and body from the moving chain 20.

A blade or bar 21 is provided for supporting the chain 20 and is mounted upon the frame 11 by means of a pair of spaced studs 22. The studs 22 are threaded and project perpendicularly from the flat frame portion 17. The cover plate 25 is i'lxed in position upon the studs 22 by nuts 23 whereby the cover plate protects the users hands and body from the moving chain 20. The blade 21 is provided with an elongated slot 26 through which the studs 22 project. The studs project through suitable bores 27 in the cover plate and extend through a ribbed portion 30 on the back of the cover plate as illustrated in FIGURE 4. Received between the studs 22 is a spacer 31. The spacer 31 may be adjustable as to length as illustrated or may be similar to the spacer 31 illustrated in my prior Patent 3,194,284, As is best illustrated in FIGURE 3, the: spacer 31 has a thickness which is greater than the blade 21. Consequently, when the nuts 23 are tightly threaded up against the cover plate, the cover plate is still held in sufficiently spaced relation relative to the frame 11 to permit reciprocation of the blade 21 upon the studs. At the distal end of the blade 21, there is provided a pulley 32 upon which the chain rides. The chain is driven by a drive sprocket 35 rotatably mounted upon a frame and driven by the motor 12.

The present invention uses the concept of maintaining a spring tension against the blade 21 to urge it away from the drive sprocket 35 and to maintain the chain tight. The present invention further includes the concept of providing adjustment means for adjusting the spring action in order that the chain tension can be adjusted to a desired value. This concept is embodied in the structure primarily illustrated in FIGURES 2 and 4. Referring to FIG- URE 4, the ribbed portion 30 defines a recess 36 which opens inwardly and receives a screw 37 which extends generally parallel to the slot 26 and to the direction of reciprocation of the bar 21. The screw 37 also extends through coaxial apertures 40 in the ribbed portion 30 and bears against the abutment surface 41 on the ribbed portion. The screw 37 has a pair of heads 42 and 45 both of which `are located outside of the ribbed portion 30 and which can bear against the ribbed portion. The screw 37 has threadedly received thereon an internally threaded lug member 46 which has a projection lug 47 integral therewith. The lug 47 projects perpendicularly relative to the blade 21 into a suitable aperture 50 through the blade, the suitable aperture having the same configuration, that is, cylindrical, as the lug 47.

Fixed to the end of the screw 37 and coaxial therewith is an extension 51 at the distal end of which there is mounted a head 52 having a plurality of tapered teeth 53. The head 52 along with a further head 5S also having tapered teeth 56 forms a clutch. The head 55 has an aperture therethrough through which extends the extension 51, said aperture being suiciently large that the head 55 is loosely received on the extension 51. A coil spring 57 is xed at one end to the rib 30 and at the other end to the clutch portion 55.

FIGURE 4 shows the device in a nonoperating position, that is with the two portions 55 and 52 of the clutch 60 separated from one another. In actual operation of the device unless the two clutch portions are held apart by some sort of tool, the spring 57 through its resilient action holds the clutch portion 55 in engagement with the clutch portion 52.

In order to operate the present device, the user moves the lug member 46 longitudinally of the screw 37 by rotating the head 52. This can be accomplished by means of a suitable wrench. The head 52 is rotated and the lug member 46 moved in a suitable direction which would be leftwardly as viewed in FIGURE 4 until the blade 21 suiciently tightly engages the chain 20 to provide a proper tension in the chain. The head 52 is held in such position and the head S is then rotated as far as the head 55 can be rotated and the clutch still hold. In other words, if the screw 37 is turned, for example, clockwise to adjust the position of the lug member, then the portion 55 of the clutch is turned counterclockwise as far as the click action of the clutch will hold. As a nal step, the person adjusting the device removes his hold from the heads 52 and 55. It will be noted that the spring action in the spring 57 will act to hold the tension in the bar 21 of the chain saw. As the chain becomes worn the spring 57 tends to rotate the head 52 thus taking up the slack produced by the wearing of the device and maintaining tension on the chain.

It will be evident from the above description that the present invention provides an improved c'hain saw tensioning device. It will also be obvious from the above description that the present invention provides a chain saw teusioning device which is operable to set the chain tension at a desired v alue and which is also operable to maintain the tension on the chain.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrated and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modications that come within the spirit of the invention and the scope of the claims are also desired to be protected.

The invention claimed is:

1. In a chain saw including an endless toothed chain, a frame, a drive sprocket rotatably mounted on said iframe and supporting said chain, a pair of spaced threaded studs xed to said frame, a blade having an elongated slot and received on said studs with the studs projecting through said slot, a guard cover received on said studs, nuts retaining said `cover on said studs, a spacer having a thickness greater than the thickness of said blade and received between said frame and cover and spacing said cover from said frame a sucient distance to permit reciprocation of said blade on said studs, said blade providing supporting means for said chain, the improvement which comprises: a screw rotatably mounted on and extending through said cover and having an enlarged headed end bearing against said cover, a lug member threadedly received on said screw, said lug member having a lug projecting perpendicularly of said blade, said blade having an aperture receiving the lug of said lug member, said screw having an extension secured thereto which is coaxial with said screw, a coil spring coiled about said extension and xed at one end to said cover, a clutch including two portions one of which is xedly mounted on the distal end of said spring and the other of which is iixedly mounted on said extension, said coil spring acting to resiliently hold said clutch portions in engagement with one another, said clutch portions being capable of holding in the same relative position to one another against forces below a given magnitude tending to rotate one portion relative to the other, but arranged to permit relative rotation of said portions in response to forces above said given magnitude tending to rotate one portion relative to the other.

2. The chain saw arrangement of claim 1 wherein said clutch portions each have a plurality of tapered teeth, the teeth of one portion normally engaging the teeth of the other portion in order to resist relative rotation between said portions.

3. The chain saw arrangement of claim 1 wherein said coil spring has a resilient bias therein tending to rotate said clutch and screw and to force said blade against said chain to take up slack in said chain.

4. The chain saw arrangement of claim 1 wherein said screw has `a pair of nonthreaded bearing portions which rotatably engage said cover, said screw also having a pair of heads, said cover having a pair of projecting `portions through which said screw extends with a recess therebetween, said screw heads being located outboard of said projecting portions and acting to retain said screw rotatably mounted on said cover, said lug member being received within said recess.

5. The chain saw arrangement of claim 4 wherein said clutch portions each have a plurality of tapered teeth, the teeth `of one portion normally engaging the teeth of the other portion in order to resist relative rotation between said portions.

6. The chain saw arrangement of claim 5 wherein said coil spring has a resilient bias therein tending to rotate said clutch 'and screw and to force said blade against said chain to take up slack in said chain.

References Cited UNITED STATES PATENTS 2,910,099 10/1959 Mall 143-32 3,194,284 7/1965 Walker 143--32 3,382,898 5/1968 Walker 143-32 DONALD R. SCHRAN, Primary Examiner. 

